Optical fiber connectors are an essential part of substantially all optical fiber communication systems. For instance, optical connectors are used to join segments of fiber into longer lengths, to connect fiber to active devices such as radiation sources, detectors and repeaters, and to connect fiber to passive devices such as switches and attenuators. The principal function of an optical fiber connector is to hold a fiber end such that the core of the fiber is axially aligned with the optical path of the component to which the connector is mated (e.g., another fiber, a planar waveguide, or an opto-electric device). This way, light from the fiber is optically coupled to the other component.
It is well known that to effect optical coupling and minimize Fresnel loss, “physical contact” may be made between the fiber end face and the optical path of the mating device. To effect physical contact, traditionally optical connectors have employed a “ferrule,” which is a well-known component for holding one or more fibers such that the fiber end faces are presented for optical coupling. Ferrule connectors typically bias the ferrule forward such that, when the connector is mated to a mating component, the ferrule urges against the mating component to physically contact the fiber end face with the optical path of the mating component.
To effect such physical contact, a conventional ferrule typically requires polishing. A polished ferrule may best be described by way of contrast to an unpolished ferrule. An unpolished ferrule has a geometry and anomalies on its end face which make it difficult, if not impossible, to bring the end face of fiber housed therein into physical contact with the optical path of the mating component. In addition, when multiple fibers are affixed to an unpolished ferrule, the position of the fiber end faces tend to vary along the mating axis, thereby making it difficult to effect optical coupling with all of the fibers. Polishing the end face of the ferrule with the fibers held therein, shapes and smoothes the ferrule end face while simultaneously polishing the fiber end faces and making them coplanar. To minimize variances in the shape of the ferrule and the coplanarity of the fiber end faces, polishing typically is performed to exacting standards. Polishing therefore tends to be costly and prone to reworking and waste, thereby lowering yields. The problems associated with polishing the ferrule are exasperated in multi-fiber ferrules which are more complicated to polish.
This issue was addressed in U.S. Pat. No. 7,377,700, which discloses an approach for producing a ferrule assembly using an unpolished assembly. Briefly, the approach involves (a) positioning at least one fiber in a ferrule such that a portion of the fiber extends beyond the end face of the ferrule; (b) affixing the fiber relative to the ferrule; and (c) cleaving the portion of the fiber. Such an approach is beneficial because it separates the functions of preparing the fiber's end face for optical coupling and positioning the fiber within the ferrule. By treating these functions separately, the fiber end face can be prepared independently of the ferrule, thereby eliminating the need to polish the ferrule/fiber assembly, while facilitating the precise positioning of the fiber end face relative to the ferrule. This patent recognizes also that it is generally preferred to have the fiber end face protrude from the ferrule to enhance its ability to make physical contact.
Although this approach offers significant advantages, applicants recognize that coplanarity among the fibers tends to become problematic as the number of fibers in the ferrule increases. That is, cleaving fibers and positioning them in the ferrule such that all the fiber end faces are essentially in the same plane is very difficult when the fibers are not polished in situ in the ferrule. This difficultly increases necessarily as the number of fibers increases. The issue of coplanarity is addressed in United States Patent Application No. 20090271126, incorporated by reference.
Therefore, there was a need for a process of producing a ferrule assembly in which precise fiber protrusion is achieved among the fibers without polishing. This need and others was addressed in U.S. patent application Ser. No. 12/872,315, which discloses a ferrule assembly in which the protrusion of the cleaved fibers is established by using a tool that has a register surface and one or more alignment members that cooperate with one or more alignment members of a ferrule to align the register surface of the tool with the ferrule end face, and thereby provide a register surface against which each fiber can abut to ensure its proper protrusion. Proper fiber protrusion facilitates physical contact among the fibers as described above.
Although the approach in the '315 patent application facilitates good fiber end face coplanarity, it is likely that, at the microscopic level, the fiber ends may not be truly planar or in the same plane as the surface of the ferrule. Accordingly, there is a need for an approach that improves the quality of the mating surface of a connector. The present invention fulfills this need among others.